I have been running Mobil 1 in all of my Volvos. I know my V50 has regular oil in it and I want to switch to synthetic. I live in the SE when it can get above 90 degrees for extended periods of time during the summer. The V50 owner's manual says to use 40 weight oils over 86 degrees Fahrenheit. Mobil suggests a 5W-30W for the V50. Keep in mind my summers are hot and winters mild with the lowest temps in the +teens and 20s Fahrenheit. What viscosity oil should I use?

I know Volvo recommends Castrol but I figure that is just a marketing ploy. The Mobil 1 0-40 weight is formulated for European cars.

which oil should I use?
John

 

Perfect!

 

Here in MD I run 5W30 Mobil 1 Synth in the winter and 10W30 in the summer. No problems.
Stan